1. Field of the Invention
The present invention generally relates to a wrenching tong and other power tongs. Particularly, the present invention relates to a wrenching tong for use in making or breaking tubular connections. More particularly still, the present invention relates to a tong which has been adapted to reduce the likelihood that it will damage pipe connections.
2. Description of the Related Art
In the construction of oil or gas wells it is usually necessary to construct long drill pipes. Due to the length of these pipes, sections or stands of pipe are progressively added to the pipe as it is lowered into the well from a drilling platform. In particular, when it is desired to add a section or stand of pipe the string is usually restrained from falling into the well by applying the slips of a spider located in the floor of the drilling platform. The new section or stand of pipe is then moved from a rack to the well center above the spider. The threaded pin of the section or stand of pipe to be connected is then located over the threaded box of the pipe in the well and the connection is made up by rotation therebetween. An elevator is connected to the top of the new section or stand and the whole pipe string lifted slightly to enable the slips of the spider to be released. The whole pipe string is then lowered until the top of the section is adjacent the spider whereupon the slips of the spider are re-applied, the elevator disconnected and the process repeated.
It is common practice to use a power tong to torque the connection up to a predetermined torque in order to make this connection. The power tong is located on the platform, either on rails, or hung from a derrick on a chain. In order to make up or break out a threaded connection, a two tong arrangement is necessary. An active (or wrenching) tong supplies torque to the section of pipe above the threaded connection, while a passive (or back up) tong supplies a reaction torque below the threaded connection. The back up tong clamps the pipe below the threaded connection, and prevents it from rotating. This clamping can be performed mechanically, hydraulically or pneumatically. The wrenching tong clamps the upper part of the connection and is driven so that it supplies torque for a limited angle.
This power tong arrangement is also used to torque up connections between other tubulars, for example casing and tubing.
Normally, in order to supply high torque, the wrenching tong is driven hydraulically. One or two hydraulic cylinders drive the tong through a small angle, typically in the region of 25xc2x0, depending on the tong design. Due to the geometric configuration normally used, the torque output of the tong changes as a sine function of the angle driven, which results in a reduction of torque output across the drive angle of up to 15%.
In order to make up or break out a connection of modem drill pipe or casing, high torque must be supplied over a large angle. This angle is sometimes six times higher than a conventional wrenching tong can supply. In order to overcome this, the wrenching tong must grip and wrench the tubular several times to tighten or break the threaded connection fully. This has a number of disadvantages. The action of gripping and releasing the pipe repeatedly can damage the pipe surface. Due to the high costs associated with the construction of oil and gas wells, time is critical, and the repeated clamping and unclamping of the wrenching tong greatly increases the time taken to attach each new section or stand of tubulars. It also has the effect that the torque provided is discontinuous, increasing the difficulty of accurately controlling the torque with respect to the angle turned.
Further, the drill pipe may be damaged if the torque applied is above the predetermined torque for making or breaking the connection. Generally, drill pipe connections are designed to makeup or breakup at a predetermined torque. Thus, if too much torque is applied, the connection may be damaged. Conversely, if insufficient torque applied, then the drill pipes may not be properly connected.
Therefore, there is a need for an improved apparatus for making or breaking a tubular connection. Further, there is a need for an apparatus that will makeup or breakup a tubular connection with minimal gripping and releasing action. Further still, there is a need for an apparatus for monitoring and controlling the torque applied to making or breaking a tubular connection.
According to a first aspect of the present invention there is provided apparatus for applying torque to a first tubular relative to a second tubular, the apparatus comprising a first tong for gripping the first tubular and a second tong for gripping the second tubular, wherein the first tong is provided with teeth around a peripheral surface thereof, the second tong is provided with at least one pinion, and the pinion meshes with the teeth in such a way that the first tong and the second tong can be rotated relative to one another when the pinion is rotated.
Preferably the first tong is a back-up tong and the second tong is a wrenching tong. Both tongs are preferably substantially cylindrical, and an axial passage is preferably provided therethrough for receiving tubulars. A passage is preferably provided from a peripheral edge to the axial passage of each tong to allow the introduction of tubulars into the axial passage. The pinion is preferably located at or near the periphery of the second tong. A motor may be provided on the second tong and coupled to the at least one pinion.
The second tong is preferably provided with two pinions, although in another embodiment it may be provided with only one. The pinions are preferably located at or near the periphery of the second tong spaced by substantially 180xc2x0 about the longitudinal axis of the tong. In another embodiment they may be spaced by substantially 120xc2x0 about the longitudinal axis of the tong.
Preferably, the first tong comprises a plurality of hydraulically driven clamping jaws for gripping the first tubular and the second tong comprises a plurality of hydraulically driven clamping jaws for gripping the second tubular. Each jaw may be equipped with two or more dies, and is preferably attached to hydraulic driving means via a spherical bearing, although the jaw may be an integral part of the hydraulic driving means.
Bearings supported on resilient means are preferably provided between the first tong and the second tong to facilitate relative axial movement of the first and second tongs.
According to a second aspect of the present invention there is provided apparatus for applying torque to a first tubular relative to a second tubular, the apparatus comprising a gear and at least one pinion, and first clamping means for clamping the first tubular within the gear, the pinion being attached to second clamping means for clamping the second tubular, and the pinion meshing with the gear in such a way that the first clamping means and the second clamping means can be rotated relative to one another by rotating the pinion.
The first clamping means preferably comprise jaws mounted within the gear about an axial passage extending through the gear. The second clamping means preferably comprises jaws mounted within a clamping housing about an axial passage extending therethrough. A motor is preferably fixed to the clamping housing and coupled to the or each pinion.
According to a third aspect of the present invention there is provided a method of applying torque to a first tubular relative to a second tubular, the method comprising: clamping the first tubular in a first tong; clamping the second tubular in a second tong; and rotating a pinion connected to the second tong and which meshes with teeth provided around a peripheral surface of the first tong so as to rotate the first tong relative to the second tong.
According to a fourth aspect of the present invention there is provided a method of coupling a tool to a length of tubular, the method comprising the steps of:
securing the tool in a basket;
lowering a tong arrangement having a rotary part and a stationary part, relative to the basket to engage respective locking members of the tong arrangement and the basket, thereby fixing the basket and the tool relative to the stationary part of the tong arrangement; and
rotating the length of tubular using the rotary part of the tong arrangement so as to couple the tool to the length of tubular.
This method may be used to couple a tool such as a drill bit, to a length of drill pipe. The coupling portion of the length of drill pipe may be brought into proximity with a corresponding coupling portion of the tool either before or after the lowering of the tong arrangement.
The length of drill string may be gripped by the rotary part of the tong arrangement either before or after the lowering of the tong arrangement. The length of drill string may be located proximate to the basket containing the tool either before or after the string is gripped by the rotary part of the tong arrangement.
By carrying out the steps of the above fourth aspect of the present invention in reverse (including rotating the length of tubing in the opposite direction), a tool may be decoupled from a length of tubular.
According to a fifth aspect of the present invention there is provided apparatus for enabling a tool to be secured to a length of drill pipe, the apparatus comprising:
a basket arranged to securely retain the tool;
a tong arrangement having a rotary portion and a stationary portion, the rotary portion being arranged in use to grip and rotate the length of tubular; and
first locking means provided on the basket and second locking means provided on the stationary portion of the tong arrangement, the first and second locking means being engageable with one another to fix the basket relative to the stationary portion of the tong arrangement.
Preferably the first and second locking means are engageable and disengageble by means of linear movement of the tong arrangement relative to the basket.
Preferably, the basket is arranged to prevent rotation of the tool in the basket, wherein in use the rotary portion of the tong arrangement may be used to rotate the length of drill pipe to secure a screw connection between the length of drill pipe and the tool.
Preferably, one of the first and second locking means comprises one or more slots, and the other of the first and second locking means comprises one or more projecting members, the slots and the members being engageable and disengageable by relative linear movement of the tong arrangement and the basket.
According to a sixth aspect of the present invention there is provided a tong for use in clamping a length of tubular during the making up or breaking out of a connection, the tong comprising:
a body portion having a central opening therein for receiving a length of tubular; and
at least two clamping mechanisms mounted in said body, the clamping mechanisms being radially spaced about said opening;
a plurality of elongate mounting members disposed between each of the clamping mechanisms and the body of the tong, each mounting member having a flat face for abutting a side of a clamping mechanism and a rounded side for locating in a complimentary shaped recess in the tong body,
wherein each tong may be displaced to some extent from radial alignment with the central opening of the tong.
The present invention provides a positioning apparatus for determining the position of a tubular with respect to the tong. The positioning apparatus includes a plunger having an end contactable with the tubular disposed on a base. The plunger may be coupled to a visual indicator to indicate the axial travel of the plunger relative to the base.
In another aspect, the present invention provides a torque measuring flange for determining the torque applied by a motor to the tong. The flange includes a top plate and a bottom plate. The flange further includes one or more wedges disposed about the periphery of the flange. Preferably, two wedges are attached to the top plate and two wedges are attached to the bottom plate. One or more cylinders may be disposed between two wedges, whereby compressing the two wedges causes a piston in the cylinder to compress.
In another aspect, the present invention provides a positioning tool for positioning a tubular relative to a tong. The positioning tool includes a positioning member for determining a position of the tubular and a centering member for engaging the tubular. The positioning tool further includes means for actuating the centering member. The position of the tubular may be actively adjusted by actuating the centering member.
In another aspect, the present invention provides a method for positioning a tubular relative to a tong. The method includes engaging the tubular with a positioning member, moving the positioning member, and moving the tong.
In another aspect still, the positioning tool may further include a joint detection member. Preferably, the joint detection member includes a proximity sensor connected to a computer or other programmable medium.